Fuels and process for burning them



ice

' 3,038,300 FUELS AND PROCES FOR BURNING TELEIW I Charles John Pedersen, Salem, N..l., assignor to E. l. du

This invention relates to fuel compositions and to processes for burning them, and particularly to fuel compositrons which are activated for ignition with fuming nitric acid and to initiating the ignition of fuels in rockets and like devices.

In the operation of rockets, rocket motors and other devices containing motors operating in like manner, a liquid fuel is injected into a combustion chamber where it is ignited and burned to form large amounts of gases at high pressure which escape through an exhaust nozzle at high velocity. U ually, the liquid fuel comprises two components-a bulk fuel and an oxidizerwhich are injected into the combustion chamber separately and simultaneously. The bulk fuel usually is a normally liquid hydrocarbon such as gasoline, kerosene, benzene and the like. The oxidizer usually will be a well-known oxidizing agent such as hydrogen peroxide, nitrogen tetroxide and nitric acid. 'For many applications, white fuming nitric acid has been found to be the most satisfactory.

In the operation of such devices, particularly in the operation of rockets, it is essential that the combustion occur immediately and smoothly as the bulk fuel and the oxidizer are injected into the combustion chamber. An electrical ignition system, such as a spark plug or a hot spot, has been used to cause the combustion to start. However, difi'lculties are often encountered with such electrical systems. Such an electrical system may fail completely or give such a weak spark as to fail to ignite the fuel when such fuel is of the type most commonly employed heretofore. Such a system may miss, whereupon the fuel will build up in the combustion chamber so that, when ignition does occur, there is a destructive explosion rather than a smooth combustion. Also, in many cases, it is desirable to eliminate the electrical ignition system so as to reduce the size and weight of the rocket or like device or to increase its fuel capacity.

' It has been proposed to initiate the combustion in the combustion chamber by first introducing a compound which is hypergolic with the oxidizer, i.e., ignites spontaneously upon contact with the oxidizer, and then introducing the bulk fuel into the hot combustion chamber. See Patent No. 2,637,161 to Tschinkel. Such a system I has the disadvantage that, when the initiator is used up,

ignition within the combustion chamber is no longer assured.

It is an object of this invention to provide new and improved fuel compositions which are activated for ignition with fuming nitric acid. A further object is to provide novel methods for burning normally liquid hydrocarbon fuels which are particularly valuable for use in the operation of rockets, rocket motors and like devices. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accordance with this invention which comprises bringing together and igniting in the presence of a normally liquid hydrocarbon fuel fuming nitric acid and a solution of an organic compound which contains the'dicyclopentadienyliron nucleus in a concentration of from about to about 50% by weight in a readily combustible organic liquid solvent, and the provision of fuel compositions which are activated for ignition with fuming nitric acid and which consist essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 5% to about 50% by weight of a dissolved organic compound which contains the dicyclopentad-ienyliron nucleus.

The dicyclopentadienyliron compounds of this invention include dicyclopentadienyliron itself and substituted dicyclopentadienylirons in which the substituents are on the cyclopentadienyl rings and consist of one to four members of the class consisting of hydrocarbon radicals of l to 12 carbon atoms, monohalogenated hydrocarbon radicals of 1 to 12 carbon atoms in which the halogen atom has an atomic weight of at least 35, organic radicals consisting of 1 to '12 carbon atoms and 1 oxygen atom and the rest hydrogen atoms, amino groups, monoamino alkyl radicals of 1 to 12 carbon atoms, and a second dicyclopentadienyliron nucleus joined to the first mentioned dicyclopentadienyliron nucleus by two divalent hydrocarbon bridging radicals each of which contains 1 to 12 carbons, there being no more than 2 such substituents on any one cyclopentadienyl ring.

The substituted dicyclopcnt-adienylirons, which may be employed in accordance with this invention are members of the classes consisting of:

(1) Those in which the substituents consist of 1 to 4 hydrocarbon radicals of l to 12 carbon atoms such as bis- (methylcyclopentadienyl)iron, (ethylcyclopentadienyl) cyclopen-tadienyliron, bis(pentylcyclopentadienyl) iron, bis(diphenylcyclopentadienyl)iron and bis(dicyclohexylcyclopentadienyl)iron which may be prepared by thev methods disclosed by Graham and Whitman in their copending application Serial No. 352,294, filed April 30, 1953; (cyclopentenylcyclopentadienyl) (cyclopentadienyl)iron, a yellow crystalline solid melting at 6667 C. and (cyclopentcyclopentadienyl) (cyclopentadienylfiron, a yellow oil freezing at l516 C., boiling at -165 C. at 10 mm., giving a yellow color in sulfuric acid turning to green which are prepared by the methods disclosed by Weinmayr in his copending application Serial No. 388,703, filed October 27, 1953, now Patent No. 2,831,- 879 patented April 22, 1958; (cyclopentadienyl) (phenylcyclopentadienyDiron, bis(phenylcyclopentadienyl)iron, (4 -biphenylyleyclopentadienyl) (di 4 biphenylcyclopentadienyl)iron and bis(p-diphenylcyclopentadienyl)- iron which may be prepared by the methods disclosed by Weinmayr in his copending application Serial No. 352,- 283, filed April 30, 1953 (now abandoned);

(2) Those in which the substituents consist of a second dicyclopentadienyliron nucleus joined to the first such mucleus by two divalent hydrocarbon bridging radicals each of which contains 1 to 12 carbon atoms, such as methylene and phenylmethylene bridging radicals, which is the condensation product of two moles of dicyclopentadienyliron with two moles of an aldehyde, e.g. formaldehyde, with the elimination of two moles of water and which may be prepared by the methods disclosed by Weinmayr in his copending application Serial No. 312,851, filed October 2, 1952, now Patent No. 2,694,721. patented November 16, 1954;

(3) Those in which the substituents consist of monohalogenated hydrocarbon radicals of 1 to 12 carbon atoms in which the halogen atom has an atomic weight of at least 35 (chlorine, bromine and iodine), preferably chlorine, such as (p-chlorophenylcyclopentadienyl) (ey clopentadienylfiron and bis(p-chlorophenylcyclopenta dienyl)iron which may be prepared by the methods dis closed by Weinmayr in his copending application Serial No. 352,283, filed April 30, 1953 (now abandoned);

(4) Those in which the substituents areorganic rad icals consisting of 1 to 12 carbon atoms, 1 oxygen atom and the rest hydrogen atoms, such as the carboxaldehydem.

Patented June 12, 1962 represented by which maybe prepared by: the

1, 1953, now Patent (6) inclusive, above; and

cyclopentadienyl(aldomethylcyclopentadienyl)iron and bis(aldomethylcyclopentadienyl)iron application Serial No. 360,370,

Graham in his copending Patent ,No. 2,849,469 patented filed June 8, 1953, now August 26-, 1958; the acyl (acetylcyclopentadienyil) (cyclopentadienyl) iron w'h i c h may be prepared by the I in his copending application Serial No. 352,029, filed April 29, 1953, now Patent No. 2,988,562 patented June '13, 1961, and by bis(acetylcyclopentadienyl)iron which derivatives, represented by.

method disclosed by Neinmayr methods disclosed by tains the dicyclopentadienyliron compound in solution in a concentration of about sufficient to render the solution hypergolic with fuming produces much more vigorous fuming of the solution than, t

may be prepared by the method disclosed by Woodward et al. in J.A.C.S. 74, 3458 (1952);.the hydroxy alkyl derivatives, i represented jhahydroxyethyl cyclopentadienyl') iron which may be madeby the methods his copending application Serial No. 365,558, filedluly No. 2,810,737 patented October 22, 1957 the 'hydroxyat'yl derivatives, represented by (cyclopentadienyl) (p hydroxyp enylcyclopentadienyl)iron Serial No. 352,- 283,-fi1ed April 30, 1953 (now abandoned);

Serial No. 365,556, filed luly l, 1953;

(6) Those alkyl radicals of 1 to 12 carbon atoms, represented by (aminoethyl cyclopentadienyl)cyclopentadienyliron,

Graham and Whitman intheir copending application Serial No. 365,563,. filed July 1, 1953, now Patent No. 2,859,233 patented November 4, 1958;.

(7) Those in which there are 2 to 4 stituents selected from the class as set forth in (1) to (8) Mixtures of 2 or more of dicyclopentadienyliron and such substituted dicyclopentadienylirons.

It has been found that such organic compounds, containing the dicyclopentadienyliron nucleus, are hypergolic with fuming nitric acid. That is, when such compounds are brought into contact with fuming nitric acid, spontaneous ignition occurs immediately and combustion continues with great vigor. When fuming nitric acid is added to a normally liquid hydrocarbon fuel under standard conditions, the nitric acid oxidizes the hydrocarbon with the evolution of fumes of oxides of nitrogen but usually without spontaneous combustion. If the fuel contains as little as 0.1% by weight of dicyclopentadienyliron compound of this invention in the solid, i.e. undissolved state, dispersed in or covered by the fuel, the addition of a small proportion of fuming nitric acid thereto results in vigorous spontaneous combustion of the mixture; i.e., normally liquid hydrocarbon fuels containing at least 0.1% by weight of such dicyclopentadienyliron compounds in the solid, i.e. undissolved state are hypergolic with fuming nitric acid. Similar dispersions of solid, i.e. undissolved dicyclopentadienyliron compounds in other readily combustible organic liquids are likewise hypergolic with fuming nitric acid. By a readily combustible organic liquid or solvent, is meant one which has such characteristics of combustibility as would obviously render it suitable for use as a fuel or as a component of a fuel.

Solutions of such dicyclopentadienyliron compounds in readily combustible organic solvents, in which the dicyclopentadienyliron compound is in a concentration of at least 25% by weight, are also hypergolic with fuming nitric acid.

On the other hand, when the dicyclopentadienyliron compound is completely dissolved in a normally liquid hydrocarbon fuel or in another readily combustible or- ,disclosed by Alfred C. Haven, Jr. in

in which the-substituents are monoamino by cyclopentadienyl(hydroxy methylcyclopentadienylfiron and cyclopentadienyl(al-,

nitric acid, the additionof fuming nitric acid thereto is obtained in the absence of the dicyclopentadienyliron compound, the fuming increasing with increase in the concentration of the dicyclopentadienylironcompound in I the solution. This indicates thatthe-dicyclopentadienyliron 'cornpoundmaterially increases the rate of oxidation by the nitric acid whereby the fuelappears to be greatly I firmly believed, the mixture will be igactivated and, it is sparks, insufliciently strong to cause pound.

,which may be prepared by the .methods disclosed by j' 'Weinmayr in his, copending application The readily combustible organic liquid solvents include, in addition to such asmethyl alcohol, cthylalcoho'l; propyl alcohols, and butyl alcohols; others such as. methyl ether, ether and'dioxane', ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate, butyl acetate and anisole; amides such as N 'dimethyl. formarnide and 'N-dirnethyl acetarnide; amines such as pyridine, morignition with fuming nitric acid and which may be prepared by the methods disclosed by different 's'ub- Z pholine and'aniline; and incompletely halogenated hydrocarbons such as chloroform and monochlorobenzene.

The'novel fuel compositions, which are activated for important feature of this invention, consist essentially of l normally liquid ing from about 5% to about 50% by weightof one or more of the dicyclopentadienyliron compounds in the former asolution therein, and (3) mixtures of (1) and (2). When the dicyclopentadienyliron compound is in the solid state, the fuel composition (1) may, and usually will, contain some of the compound in solution. When the dicyclopentadienyliron compound is in the form of a solution (2), it may be dissolved in the hydrocarbon fuel alone or, in whole or in part, in another readily combustible organic solvent therefor, it being understood that the percent by weight of the dicyclopentadienyliron compound is based on the total weight of the composition of which it forms a part. Normally liquid hydrocarbon fuels in the kerosene boiling range boil in the range of from about C. to about 315 C. and include kerosene, crude or refined, and synthetic mixtures of hydrocarbons falling in that boiling range.

Dicylopentadienyliron is soluble in high concentrations in the normally liquid hydrocarbon fuels and in common organic solvents such as those listed hereinbefore as readily combustible organic liquid solvents. The substituted dicyclopentadicnylirons are of varying solubility in the fuels and some require additional solvents when it is desired to incorporate them in the fuels in high concentrations as solutions. The literature and application disclosures of the compounds and of the methods of making them, hereinbefore referred to, also disclose suitable solvents therefor, including aliphatic and aromatic hydrocarbons such as petroleum ether, gasoline, benzene and xylene; alcohols such as methyl alcohol, ethyl alcohol and butyl alcohols; ethers such as methyl ether and ethyl ether, and the like.

Broadly, the process of this invention comprises bringing together and igniting fuming nitric acid and a solution of one or more of the dicyclopentadienyliron compounds in a concentration of from about 5% to about 50% by Weight in a readily combustible organic solvent in the presence of a normally liquid hydrocarbon fuel or more by weight but indicyclopentadienyliron com the normally liquid hydrocarbon, fuels, aromatic and aliphatic hydrocarbons generally such as petroleum ether, gasoline, benzene and xylene; alcohols diethyl which-constitute an I hydrocarbon fuels containing at least 0.1% by weight of one or more of the dicyelopentadienylmore vigorously than the control.

and burning the'mixture. The means and modes for carrying out such process may be widely varied.

When the fuel composition is hypergolic with fuming nitric acid, the fuel composition and the fuming nitric acid may be fed directly, but separately, and simultaneously into the combustion chamber employing an apparatus such as that disclosed by Tschinkel in Patent No. 2,637,161, whereupon the fuel composition and the fum ing nitric acid will mix and spontaneously ignite and burn vigorously to form the large volume of gases required for propelling the rocket or like device. When the fuel composition is not hypergolic with fuming nitric acid, that is, when it contains about 5% to about 20% of a dissolved dicyclopentadienyliron compound, insufficient to render the fuel composition hypergolic, the apparatus and mode of procedure may be similar, except that the combustion chamber will be provided with a conventional electrical ignition system, including a spark plug or hot spot, to ignite the mixture of fuel composition and fuming nitric acid.

Alternatively, the rocket or similar device may be provided with a third tank feeding into the combustion chamber just ahead of the nitric acid and containing the dicyclopentadienyliron compound in powdered form or a dispersion or solution of the dicyclopentadienyliron compound in a readily combustible organic liquid in such form and concentration as to render the dispersion or solution hypergolic with fuming nitric acid. In such case, the bulk fuel may be devoid of dicyclopentadienyliron compound or contain dicyclopentadienyliron compound in an amount insufiicient to render the fuel composition hypergolic with the fuming nitric acid. Under these circumstances, the powdered dicyclopentadienyliron compound or the hypergolic dispersion or solution thereof will first contact the fuming nitric acid, ignite and burn vigorously and the bulk fuel will be fed into such burning mixture whereby the bulk fuel will also be ignited and caused to burn. Still other means or types of apparatus and procedures, for carrying out the process of this invention will be apparent to those skilled in the art.

In order to more clearly illustrate this invention and the advantageous results to be obtained thereby, the following examples are given in which the fuel is a refined kerosene which has had the aromatic and naphthenic hydrocarbons removed in order to reduce smoking tendencies and is known as JP-4 rocket fuel and which is completely described in Petroleum Processing Magazine, October 1952,'page 1426.

EXAMPLE 1 A small amount (about 20 cc.) of a kerosene based .fuel characterized as JP-4 was placed in a shallow porcelain dish. About 0.1 g. of crystalline dicyclopentadienyliron was added to the dish containing the fuel and the solid crystals allowed to settle to the bottom. Another porcelain dish containing the same rocket fuel, but without the dicyclopentadienyliron, was used as a control. Fuming nitric acid (about 1 cc.) was added to each of the two dishes. The fuel, in the dish containing the dicyclopentadienyliron in solid crystalline form, immediately burst into flames and continued to burn fiercely. The control fuel, without dicyclopentadienyliron, did not ignite.

It is thus evident that the presence of solid particles of dicyclopentadienyliron will enhance the activtiy of a rocket fuel. As already indicated, the solid compound may be dispersed in the fuel or sprayed'into the rocket combustion chamber. 7

When the experiment was repeated with a 5% solution of dieyclopentadienyliron in the fuel and fuming nitric acid as before, the fuel did not ignite, but fumed much It is thus evident that the fuel was considerably activated by the low concentration of dissolved dicyclopentadienyliron.

6 EXAMPLE 2 When cyclopentadienyl(ethylcyclopentadienyl) i r o it alone and as solutions in the fuel, was treated with fuming nitric acid as described in Example 1, the following results were obtained:

In each of (c), (d) and (e), the iron compound was completely dissolved in the fuel.

EXAMPLE 3 The experiments of Example 2' were repeated, with solutions of cyclopentadienyl(cyclopentylcyclopentadienyl)iron in the fuel, with the following results:

Table II Cyolopenta- White Weight: dienyl (cye-lo- Kerosene fuming percent pentyleyclobased fuel nitric Result of iron pentadienyD- (parts by acid derivairon (parts weight) (parts tive in by weight) by wt.) fuel (a) l 5 1 Fumed vigor- 16. 7

ously but did not fire. (b) 2 5 l Fired immed- 28. 6

atly. (0)..-. 3 5 1 do 37.5 (11)---. 5 5 1 d0 50 EXAMPLE 4 Bis(phenylcyclopentadienyl)iron was added to the kerosene based fuel in the same proportions as in Example 3 butjsince this compound was soluble in the fuel to the extent of less than 10% by weight, the compositions contained substantial amounts of the compound in solid'form. When such compositions were treated with White fuming nitric acid as in the preceding examples, they firedimmediately.

EXAMPLE 5 The experiment of Example 1 in which the iron compound was dispersed in the fuel, was repeated with acetylcyclopentadienyl(cyclopentadienyl)iron. The results obtained follows:

(a) When fuming nitric acid was added to solid acetylcyclopentadienyl(cyclopentadienyl)iron, the mass burst into flames.

(b) When fuming nitric acid Was added to a slurry of 0.5% by weight of acetylcyclopentadienyl(cyclopentadienyl)iron in JP-4, the mixture burst into flames and burned violently.

(c) When fuming nitric acid was added to a 10 so lution of the iron compound in JP-4, no ignition occurred, but much more vigorous fuming occurred in comparison to a control containing no iron compound. I

EXAMPLE 6 of nitric acid is added to the fuel near the solid, the fuel bursts into flame and burns vigorously until consumed.

EXAMPLE 7 The following compounds are used to activate LIP-4 fuel in the manner previously described: (aminocyclopentadienyl) (cyclopentadienyl)iron, (cyclopentadienyl) (p-hydroxyphenylcyclopentadienyl)iron, bis(phenylcyclopentadienyl)iron, bis( p chlorophenylcyclopentadienyl) iron, and the product of the reaction between dicyclo pentadienyliron and formaldehyde.

About 10 to 20 mg. of the solid iron derivative is covered with 3 g. of JP-4 and 0.5 to 1.0 g. of fuming nitric acid is added. In all cases, ignition occurs immediately.

EXAMPLE 8 About 15 cc. of JP-4 fuel was placed in a small poreclain dish and about cc. of an approximately 25% by weight solution of technical dicyclopentadienyliron (containing a minor but significant proportion of the more soluble bis(methylcyclopentadienyl) iron) in benzene was poured into the fuel without agitation, both the solution and the fuel being at 40 C. The added solution went to the bottom of the dish and formed a layer below the fuel. Approximately 1 cc. of fuming nitric acid was then poured down the side of the dish and, as soon as it contacted the solution layer, ignition occurred and the contents of the dish continued to burn vigorously until both the solution and the fuel were consumed.

EXAMPLE 9 When the procedure of Example 8 was repeated with the various solvents and dicyclopentadienyliron compounds listed in Table III, the same results were obtained.

Where solutions of the organoiron compound in the desired concentration cannot be made with a single solvent, mixtures of solvents can be used. To illustrate, the procedure described above was followed, according to the data in Table IV. In every case, the mixture composed of the fuel and the solution of the iron compound was hypergolic with fuming nitric acid.

Table IV Solution Solvent Mixture (Per- Concen- Iron Compound cent; by Volume) tration (Percent by Wt.)

(Acetoacetylcyclopentadienyl) Dimethyl iorrnamide/ 4O (CyclopentadienyDiron. Benzene (60/40). (Acetylcyclopentadienyl)(cyclo- Acetone/drmethyl-forrn- 25 pentadienyDiron. i amide (67/33),

Do Dicthyletherldimethyl- 25 tormamide (70/30). Do t Butyl alcohol/d1 25 ngthylformamide (67/ 3 It will be understood that the preceding examples have been given for illustrative purposes solely and that many variations and modifications can be made in the compositions, the proportions thereof and the modes and apparatus employed for bringing the fuel, the dicyclopentadienyliron compound and the fuming nitric acid together in a combustion chamber under conditions such that ignition and combustion will occur, within the scope of the general description without departing from the scope or spirit of this invention.

From the preceding disclosure, it will be apparent that, by this invention, there has been provided novel fuel compositions which have enhanced burning characteristics in contact with fuming nitric acid and which are particularly useful for use in the operation of rockets, rocket motors and like devices which are propelled or otherwise motivated by expelling, through an exhaust nozzle at high velocity, large volumes of gases formed by the combustion of a liquid fuel in a combustion chamber. Also, this invention provides a novel and valuable process for burning normally liquid hydrocarbon fuels at least in part by the action of nitric acid on a novel class of hypergolic compounds which initiate and/or greatly promote and maintain the combustion. Accordingly, it is apparent that this invention constitutes a valuable contribution to and advance in the art.

This is a continuation-inpart of my copending application Serial No. 398,425 filed December 15, 1953.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of an organic compound containing the dicyclopentadienyliron nucleus in a concentration of from about 5% to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons, said organic compound being a member of the class consisting of dicyclopentadienyliron, two dicyclopentadienyliron nuclei joined by two divalent bridging radicals selected from the group consisting of methylene and phenylmethylene radicals, and substituted dicyclopentadienylirons in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 members of the group consisting of an alkyl radical of 1 to 12 carbon atoms, a cycloalkyl radical of 5 to 6 carbon atoms, the cyclopentenyl radical, an aryl radical of 6 to 12 carbon atoms, the chlorophenyl radical, the aldomethyl radical, a lower alkylacyl radical, a lower monohydroxy alkyl radical, a monohydroxyaryl radical of the benzene series which contains 6 to 12 carbon atoms,

the amino group, and a monoaminoalkyl radical of 1 to 12 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

2. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of an organic compound containing the dicyclopentadienyliron nucleus in a concentration of from about 25% to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons, said organic compound being a member of the class consisting of dicyclopentadienyliron, two dicyclopentadienyliron nuclei joined by two divalent bridging radicals selected from the group consisting of methylene and phenylmethylene radicals, and substituted dicyclopentadienylirons in which the substituents are on the cyclopentadienyl rings and consist of 1 top4 members of the group consisting of an alkyl radical of 1 to 12 carbon atoms, a cycloalkyl radical of 5 to 6 carbon atoms, the cyclopentenyl radical, an aryl radical of 6 to 12 carbon atoms, the chlorophenyl radical, the aldomethyl radical, a lower alkyl acyl radical, a lower monohydroxy alkyl radical, a monohydroxyaryl radical of the benzene series which contains 6 to 12 carbon atoms, the amino group, and a monoaminoalkyl radical of 1 to 12 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

3. A process for burning a normally liquid hydrocarbon fuel which comprises simultaneously injecting into a combustion zone fuming nitric acid and a normally liquid hydrocarbon fuel having dissolved therein from about 5% to about 20% by weight of an organic compound containing the dicyclopentadienyliron nucleus and igniting the resulting mixture, said organic compound being a member of the class consisting of dicyclopentadienyliron, two dicyclopentadienyliron nuclei joined by two divalent bridging radicals selected from the group consisting of methylene and phenylmethylene radicals, and substituted dicyclopentadienylirons in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 members of the group consisting of an alkyl radical of 1 to 12 carbon atoms, a cycloalkyl radical of 5 to 6 carbon atoms, the cyclopentenyl radical, an aryl radical of 6 to 12 carbon atoms, the chlorophenyl radical, the aldomethyl radical, a lower alkyl acyl radical, a lower monohydroxy alkyl radical, a monohydroxyaryl radical of the benzene series which contains 6 to 12 carbon atoms, the amino group, and a monoaminoalkyl radical of 1 to 12 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

4. A process for burning a bulk fuel which is a normally liquid hydrocarbon fuel, which comprises bringing together in a combustion zone fuming nitric acid and a composition which is hypergolic with the fuming nitric acid whereby the composition spontaneously ignites and burns, and injecting the bulk fuel into the resulting burning mixture, the hypergolic composition being a solution of an organic compound containing the dicyclopentadienyliron nucleus in a concentration of from about 25% to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons, said organic compound being a member of the class consisting of dicyclopentadienyliron, two dicyclopentadienyliron nuclei joined by two divalent bridging radicals selected from the group consisting of methylene and phenylmethylene radicals, and substituted dicyclopentadienylirons in which the sub 'stituents are on the cyclopentadienyl rings and consist of 1 to 4 members of the group consisting of an alkyl radical of 1 to 12 carbon atoms, a cycloalkyl radical of 5 to 6 carbon atoms, the cyclopentenyl radical, an aryl radical of 6 to 12 carbon atoms, the chlorophenyl radical, the aldomethyl radical, a lower alkyl acyl radical, a lower monohydroxy alkyl radical, a monohydroxyaryl radical of the benzene series which contains 6 to 12 carbon atoms, the amino group, and a monoaminoalkyl radical of 1 to 12 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

5. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of dicyclopentadienyliron in a concentration of from about 5% to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols,

1 0 lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

6. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of an organic compound containing the dicyclopentadienyliron nucleus in a concentration of from 5% to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons, said organic compound being a substituted dicyclopentadienyliron in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 alkyl radicals of 1 to l2 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

7. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of cyclopentadienyl(ethyl cyclopentadienyl)iron in a concentration of from about 5% to about 50% by weight in a readily combustible organic liquid solventof the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

8. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of an organic compound containing the dicyclopentadienyliron nucleus in a concentration of from about 5% to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons, said organic compound being a substituted dicyclopentadienyliron in which the substituents are on the cyclopentadienyl rings and consist of l to 4 lower alkyl acyl radicals, there being no more than two of such substituents on any one cyclopentadienyl ring.

9. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of acetylcyclopentadienyl(cyclopentadienyl)iron in a concentration of from about 5% to about 50% by Weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

10. A process for burning a normally liquid hydrocarbon fuel which comprises injecting into a combustion zone a normally liquid hydrocarbon fuel having dissolved therein from about 5% to about 20% by weight of dicyclopentadienyliron, and simultaneously injecting into said combustion zone fuming nitric acid and igniting the resulting mixture.

11. A process for burning a normally liquid hydrocarbon fuel which comprises injecting into a combustion zone a normally liquid hydrocarbon fuel having dissolved therein from about 5% to about 20% by weight of a substituted dicyclopentadienyliron in which the sub stituents are on the cyclopentadienyl rings and consist of 1 to 4 alkyl radicals of l to 12 carbon atoms, and simultaneously injecting into said combustion zone fuming nitric acid and igniting the resulting mixture.

12. A process for burning a normally liquid hydrocarbon fuel which comprises bringing together and igniting in the presence of said fuel fuming nitric acid and a solution of bis (methylcyclopentadienyl)iron in a concentration of from about to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

13. A process for burning a normally liquid hydrocarbon fuel which comprises simultaneously injecting into a combustion zone fuming nitric acid and a normally liquid hydrocarbon fuel having dissolved therein from about 5% to about by weight of cyclopentadienyl(ethyl cyclopentadienyl)iron.

14. A process for burning a normally liquid hydrocarbon fuel which comprises simultaneously injecting into a combustion zone fuming nitric acid and a normally liquid hydrocarbon fuel having dissolved therein from about 5% to about 20% by weight of bis(methylcyclopentadienyl)iron.

15. A process for burning a bulk fuel which is a normally liquid hydrocarbon fuel, which comprises bringing together in a combustion zone fuming nitric acid and a composition which is hypergolic with the fuming nitric acid whereby the composition spontaneously ignites and burns, an injecting the bulk fuel into the resulting burning mixture, the hypergolic composition being a solution of .dicyclopentadienyliron in a concentration of from about to about by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

16. A process for burning a bulk fuel which is a normally liquid hydrocarbonfuel, which comprises bringing together in a combustion zone fuming nitric acid and a composition which is hypergolic with the fuming nitric acid whereby the composition spontaneously ignites and burns, and injecting the bulk fuel into the resulting burning mixture, the hypergolic composition being a solution of an organic compound containing the dicyclopentadienyliron nucleus in a concentration of from about 25 to about 50%by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydri'c alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons, said organic compound being a substituted dicyclopentadienyliron in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 alkyl radicals of 1 to 12 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

17. A process for burning a bulk fuel which is a normally liquid hydrocarbon fuel, which comprises bringing together in a combustion zone fuming nitric acid and a composition which is hypergolic with the fuming nitric acid whereby the composition spontaneously ignites and burns, and injecting the bulk 'fuel into the resulting burning mixture, the hypergolic composition being a solution of cyclopentadienyl(ethyl cyclopentadienyl)iron in a concentration of from about 25% to about 5 0% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates,

12 anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

18. A process for burning a bulk fuel which is a normally liquid hydrocarbon fuel, which comprises bringing together in a combustion zone fuming nitric acid and a composition which is hypergolic with the fuming nitric acid whereby the composition spontaneously ignites and burns, and injecting the bulk fuel into the resulting burning mixture, the hypergolic composition being a solution of bis(methylcyclopentadienyl)iron in a concentration of from about 25 to about 50% by weight in a readily combustible organic liquid solvent of the group consisting of hydrocarbons, lower saturated aliphatic monohydric alcohols, lower saturated aliphatic ethers, lower saturated aliphatic ketones, lower alkyl acetates, anisole, lower alkyl amides of lower aliphatic acids, pyridine, morpholine, aniline, and incompletely halogenated hydrocarbons.

19. A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25% to about 50% by weight of a dissolved organic compound containing the dicyclopentadienyliron nucleus which is a member of the class consisting of dicyclopentadienyliron, two dicyclopentadienyliron nuclei joined by two divalent bridging radicals selected from the group consisting of methylene and phenylmethylene radicals, and substituted dicyclopentadienylirons in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 members of the group consisting of an alkyl radical of 1 to 12 carbon atoms, a cycloalkyl radical of 5 to 6 carbon atoms, the cyclopenteuyl radical, an aryl radical of 6 to 12 carbon atoms, the chlorophenyl radical, the aldomethyl radical, a lower alkyl acyl radical, a lower monohydroxy alkyl radical, a monohydroxyaryl radical of the benzene series which contains 6 to 12 carbon atoms, the amino group, and a monoaminoalkyl radical of 1 to 12 carbon atoms, there being no more than two of such substituents on any one cyclopentadienyl ring.

20. A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25 to about 50% by weight of dissolved dicyclopentadienyliron.

21. A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25 %to about 50% by weight of a dissolved substituted dicyclopentadienyliron in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 alkyl radicals of 1 to 12 carbon atoms.

22. A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25% to about 50% by weight of a dissolved substituted dicyclopentadienyliron in which the substituents are on the cyclopentadienyl rings and consist of 1 to 4 lower alkyl acyl radicals.

23. A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25% to about 50% by weight of dissolved cyclopentadienyl(ethyl cyclopentadienyDiron.

247 A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25% to about 50% by weight of dissolved bis methylcyclopentadienyl) iron.

25. A fuel composition hypergolic with fuming nitric acid which consists essentially of a normally liquid hydrocarbon fuel in the kerosene boiling range containing from about 25% to about 50% by weight of dissolved acetylcyclopentadienyl(cyclopentadienyl)iron.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,038,300 June 12 1962 Charles John Pedersen It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 35, for "(cyclopentcyclopentadienyl)" read (cyclopentylcyclopentadienyl) column 2, line 43, for

"(di4biphenylcyclo" read (di4biphenylylcyclo column 10, line 9, after "from" insert about Signed and sealed this 16th day of October 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A PROCESS FOR BURNING A NORMALLY LIQUID HYDROCARBON FUEL WHICH COMPRISES BRINGING TOGETHER AND IGNITING IN THE PRESENCE OF SAID FUEL FUMING NITRIC ACID AND A SOLUTION OF AN ORGANIC COMPOUND CONTAINING THE DICYLOPENTADIENYLIRON NUCLEUS IN A CONCENTRATION OF FROM ABOUT 5% TO ABOUT 50% BY WEIGHT IN A READILY COMBUSTIBLE ORGANIC LIQUID SOLVENT OF THE GROUP CONSISTING OF HYDROCARBONS, LOWER SATURATED ALIPHATIC MONOHYDRIC ALCOHOLS, LOWER SATURATED ALIPHATIC ETHERS, LOWER SATURATED ALIPHATIC KETONES, LOWER ALKYL ACETATES, ANISOLE, LOWER ALKYL AMIDES OF LOWER ALIPHATIC ACIDS, PYRIDINE, MORPHOLINE, ANILINE, AND INCOMPLETELY HALOGENATED HYDROCARBONS, SAID ORGANIC COMPOUND BEING A MEMBER OF THE CLASS CONSISTING OF DICYCLKOPENTADIENYLIRON, TWO DICYCLOPENTADIENYLIRON NUCLEI JOINED BY TWO DIVALENT BRIDGING RADICALS SELECTED FROM THE GROUP CONSISTING OF METHYLENE AND PHENYLMETHYLENE RADICALS, AND SUBSTITUTED DICYCLOPENTADIENYLIRONS IN WHICH THE SUBSTITUTES ARE ON THE CYCLOPENTADIENYL RINGS AND CONSIST OF 1 TO 4 MEMBERS OF THE GROUP CONSISTING OF AN ALKYL RADICAL OF 1 TO 12 CARBON ATOMS, A CYCLOALKYL RADICAL OF 5 TO 6 CARBON ATOMS, THE CYCLOPENTENYL RADICAL, AN ARYL RADICAL OF 6 TO 12 CARBON ATOMS, THE CHLOROPHENYL RADICAL, THE ALDOMETHYL RADICAL, A LOWER ALKYLACYL RADICAL, A LOWER MONOHYDROXY ALKYL RADICAL, A MONOHYDROXYARYL RADICAL OF THE BENEZENE SERIES WHICH CONTAINS 6 TO 12 CARBON ATOMS, THE AMINO GROUP, AND A MONOAMINOALKYL RADICAL OF 1 TO 12 CARBON ATOMS, THERE BEING NO MORE THAN TWO OF SUCH SUBSTITUENTS ON ANY ONE CYCLOPENDTADIENYL RING. 